We have a 2 year old male chocolate lab who up to now has been very happy and well behaved. We had friends visiting a couple of weeks ago with their neutered spaniel and our dog spent the entire weekend trying to mount him. Since then he has been very disobedient, and has occasionally run away after castrated male dogs he came across at our usual dog walking venue. It all came to a head today when he was chasing yet another male dog and he actually made an elderly gentleman slip and fall by running in front of him. I have an appointment for the vet tomorrow but wondered if anyone had any advice.